Add BUILTIN\Administrators as a sysadmin is MSSQL. This was broken/fixed, depending on your POV, in newer versions of SQL server. This will restore it. Be aware, this is a security risk and was changed for a reason.
EXEC sp_grantlogin 'BUILTIN\Administrators'
EXEC sp_addsrvrolemember 'BUILTIN\Administrators','sysadmin'